Our overall objective is to understand which tumor cell behaviors contribute to invasion and metastasis. Such a dissection would allow for rationale approaches to limit these aspects of tumor progression that are responsible for the greater part of cancer morbidity and mortality. While great strides are being made in our understanding of critical molecular determinates, the currently accepted experimental assessments of tumor invasion are limiting in the dissection of complex cellular responses. Quantal advances would be enabled by new assay systems that combine the best attributes of direct manipulation of the tumors and host, long-term (days to weeks) visualization of the processes, and tissue relevant relationships and architecture. Our central premise is that an ex vivo organotypic liver tissue system can provide an environment to study tumor cell invasion and metastasis. Prior works have shown that physiologically active and anatomically representative liver tissue can be recreated ex vivo from component cells. Liver is a major site of metastatic spread for many carcinomas including those of the colon, breast and prostate. Of key importance to our currently funded parental grant, is that the progression of these tumors is driven, at least in part by dysregulated signaling from the EGF receptor. We and others have shown that abrogating aspects of EGFR signaling decreases tumor invasiveness and metastasis in these tumor types, providing us with controlled tumor cell line pairs with which to validate our liver organotypic bioreactor as a model system of tumor invasion and metastasis. We propose to: Aim 1. Construct an organotypic liver tissue culture containing hepatocytes and endothelial cells. We will build upon a first generation ex vivo liver tissue system of differentiated and functional hepatocytes by adding an endothelial cell layer. After establishing this with rat liver cells, we will convert this to an all-human system. Aim II. Determine whether an organotypic liver tissue culture recapitulutes tumor cell invasion. Aim III. Determine whether an organotypic liver tissue culture supports metastatic growth. The successful completion of these Aims will provide a new ex vivo tissue model for tumor progression. Further investigations will determine key rate-limiting steps during extravasation and metastatic growth, such as adhesion, motility, or mitogenesis. Lastly, this system will then be exploited as a vehicle for therapeutic interventions, one that accounts for the agent's effect on both the tumor and host tissue.